Determination of age 2 (Radio-41) How many 14C atoms contain 1 g of carbon, which is 5730 years old. Note: a current ('today') sample has a ratio of 14C/12C to 1.2·10-12.

  Exercise: Radio-41    

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How many ¹⁴C atoms contain 1 g of carbon, which is 5730 years old. Note: a current ('today') sample has a ratio of ¹⁴C/¹²C to 1.2·10^-12.

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Hinweis: The (necessary) molar mass of ¹²C is 12.00000000000 g/mol.

Solution:

1 g^12C contains as many atoms: n=m/M= 1/12 mol or 5.018·10²²¹²C atoms
After 5730 years, a HWZ is over. So the ratio is only half as big as before.
It applies: ¹⁴C/¹²C = x = ½ · 1.2·10^-12
14C = ½ · 1.2·10^-12 · ¹²C = ½ · 1.2·10^-12 · 5.018·10²² = 3.0·10¹⁰

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